Motorized portable blower apparatus

ABSTRACT

A portable blower, and a fan for such a blower, are disclosed in which a plurality of blades extend from one side of a generally flat fan disc. The blades are swept rearwardly relative to the intended direction of rotation of the fan disc. The blades extend from the disc and are tilted transversely and in the direction of rotation of the disc. The tilt arises either due to manufacture or rotation of the disc and constitutes an air scoop for the fan.

BACKGROUND OF THE INVENTION

The present invention relates to motorized portable blowers of the typeused to blow leaves, grass clippings, etc. into a heap for subsequentdisposal and, in particular, to hand held blowers. Such devices are usedto maintain yards and gardens in a clean and tidy state, and includeback pack style blowers as well as the more numerous hand held blowers.

A typical prior art blower 101 is illustrated in FIG. 1 and essentiallyconsists of a small motor in the form of an internal combustion engine105 (either 2 stroke or 4 stroke) which has a fan mounted on its outputshaft. Both the motor and the fan are contained within a housing 102which has a handle 103 on top which enables the device to be carried.The device has a grille 106 with an array of small openings which coversa central air intake through which air enters to the fan. A single tube111 constitutes the exit path for the air exiting the blower. Manymanufacturers compete in this market and competition is intense both interms of performance and price.

These devices are used predominantly for lawn and garden tasks and havebeen available in the marketplace for about 40 years following thedevelopment over the last 50 years of portable small lightweightgasoline powered engines. There are also electric powered units poweredeither from a mains supply or battery power.

However, gasoline blowers are now very common and consist of thegasoline engine connected to an impeller type fan that is housed in afan housing. There is a generally central air inlet into the blowercasing and a peripheral outlet of the fan housing connected to an inlinerigid tube (generally formed in two parts) to direct the high speed airflow in the direction desired by the operator. This direction is changedby changing the direction or orientation of the entire hand held blower.

These devices are used, for example, to blow leaf and/or grass cuttingsto a corner of a yard for easy collection for disposal (e.g.composting). Another use is to clean leaves and other debris from hardsurfaces, paths, driveways and the like, quickly and efficiently withoutthe wasteful use of water as occurs with hosing etc.

Another use is, for example, the cleaning of stadia and parks of litterleft behind after a game or concert by blowing this rubbish into heapsfor collection and disposal.

By far the largest use is by home owners for their own yard cleaning andmaintenance jobs. Worldwide more than a million units are made everyyear and every manufacturer is trying to produce more powerful blowers.

The genesis of the present invention is a desire to improve theperformance of existing portable hand-held blowers and, in particular,to increase the overall effectiveness of the blower.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention there isdisclosed a portable hand-held blower comprising:

a power source having an axis of rotation,

a fan mounted on said power source to be driven thereby and locatedwithin the housing, said housing having an array of inlet apertures anda single main exit,

a handle atop said housing and mounted substantially above the centre ofgravity of said blower,

said main exit having a generally S-shaped configuration tosubstantially align the path of air exiting said blower with said handleto prevent a torque being experienced by an operator holding said handlein use, and

said fan being moulded in a single piece from substantially rigidmaterial;

wherein said fan comprises:

a generally flat disc each quadrant thereof having a plurality ofgenerally radially extending blades which all extend on the same side ofsaid disc,

which all are rearwardly swept relative to the intended direction ofrotation of the disc,

which all extend to a predetermined height above a plane passing throughsaid disc and substantially perpendicular to said axis of rotation,

said blades being tilted transversely and in the direction of rotationof said fan either as a consequence of the manufacture of said blades,or as a consequence of the forces created by the operational rotationalspeed of said fan, and

whereby each transversely tilted blade and its adjacent portion of saiddisc in front of each said blade forms an air scoop for said fan.

In accordance with a second aspect of the present invention there isdisclosed a fan for a blower, said fan comprising:

a generally flat disc each quadrant thereof having a plurality ofgenerally radially extending blades which all extend on the same side ofsaid disc,

which all are rearwardly swept relative to the intended direction ofrotation of the disc,

which all extend to a predetermined height above a plane passing throughsaid disc and substantially perpendicular to said axis of rotation,

said blades being tilted transversely and in the direction of rotationof said fan either as a consequence of the manufacture of said blades,or as a consequence of the forces created by the operational rotationalspeed of said fan, and

whereby each transversely tilted blade and its adjacent portion of saiddisc in front of each said blade forms an air scoop for said fan.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe appended drawing figures wherein like numerals denote like elements.

FIG. 1 is a plan view of a prior art blower.

FIG. 2 is a side view of the blower of the preferred embodiment showingthe air intake to the housing.

FIG. 3 is a plan view of the blower of FIG. 2 showing its carryinghandle and air exit tube aligned therewith.

FIG. 4 is a schematic side elevation showing a test rig set up whichenables the air thrust of various blowers to be compared.

FIG. 5 is a plan view of the fan of a first embodiment showing theblades thereon.

FIG. 6A is a side elevation of the fan of FIG. 5, showing theconfiguration of the fan when stationary, and FIG. 6B is the same sideelevation but when the fan is operating.

FIG. 7 is a vector diagram illustrating the components of therotationally induced force applied to the blades.

FIGS. 8, 9A and 9B are equivalent views to FIGS. 5, 6A and 6B but inrespect of a fan of a second embodiment.

FIG. 10 is a plan view of a fan of a third embodiment.

FIG. 11 is a side elevation of the fan of FIG. 10 when stationary.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As seen in FIGS. 2 and 3, the blower 1 of the preferred embodiment hasan exterior housing 2 which has a handle 3 located on top of the housing2. The handle 3 is positioned above the centre of gravity of the blowerand has a longitudinal axis 4. The housing has an inlet grille 6 havinga plurality of small openings through which air is sucked by a fan 7which is mounted on the output shaft of an internal combustion engine 5.

The housing 2 also has a main air exit 9 which is connected by means ofa generally S-shaped bend 10 to an air exit tube 11 which is alignedwith the longitudinal axis 4 of the handle 3. The air exit tube 11 ispreferably formed from two sections 12 and 13 each of which isdetachable from the other and from the remainder of the blower 1. Thisenables the blower to be assembled into a compact unit fortransportation and/or storage.

In operation, air is sucked through the air inlet grille 6 and expelledvia the main air exit 9 and air exit tube 11 whilst the entire blower isheld in one hand of the operator with the arm extended downwardly sothat the blower is typically about knee height. In some instances, asmall amount of air, which is intended to cool the internal combustionengine, is directed from the housing 2 via various minor air exits.

As shown in FIG. 3, it is very desirable that the air exit tube 11 bealigned with the handle 3. If this is not the case (as illustrated inFIG. 1 in which case the tube 111 is a prolongation of the air exit),this results in a net torque being applied to the handle 103 by the airexiting the tube 111. This torque resulting from the blower type in FIG.1, must then be resisted by muscular action of the wrist of theoperator. The more powerful the air thrust, the greater the torque to beresisted, and hence the more resistance required from the wrist musclesof the operator. The need for such a wrist action is avoided by havingthe air exit tube 11 aligned with the handle 3 as illustrated in FIG. 3.

However, this desirable alignment comes with an operational penalty inthat the S-shaped bend 10 constitutes a “chicane” which reduces thevelocity and force of the air exiting the blower 1.

The performance of various blowers available on the market variesconsiderably based on subjective tests in using different commerciallyavailable types of blowers to clean leaves, etc. in the private homes ofthe inventors. However, in order to provide an objective assessment ofblower performance, an air thrust test rig 15 as illustrated in FIG. 4was constructed. The test rig 15 consists of an L-shaped frame 16 havinga base 17 upon which a digital kitchen scale 18 was securely mounted.The L-shaped frame 16 also includes an upright 20 having two ballbearings one at each end of a horizontal pivot shaft 21.

A sub-assembly 23 was formed from a slightly curved rectangular plate 24which is securely connected to a force arm 25. The force arm 25 has aball bearing 26 rotatably mounted at its free end. The entiresub-assembly 23 is pivoted on its ball bearing mounted pivot shaft 21.In order to carry out a test, the free end of an air tube 212, being 270mm in length and 69 mm in interior diameter, is positioned at a fixeddistance of 100 mm from the rest position of the rectangular plate 24,this rest position being illustrated in solid lines in FIG. 4.

The receiving end of the rigidly mounted tube has an expanding femaletaper to accept the end of each single exit tube 12 of each blower beingtested. The rigid tube internal diameter is slightly larger than theexternal diameter of each of the exit tubes of the blowers under test,thus preventing any restriction of the air thrust of the blower undertest.

The thrust of the air exiting towards the rectangular plate 24 pivotsthe rectangular plate 24 in an anticlockwise direction as seen in FIG. 4into a deflected position illustrated by broken lines in FIG. 4. As aconsequence, the force arm 25 similarly rotates in a counter-clockwisedirection so that the ball bearing 26 rolls a short distance (e.g. 1 mm)over the top of the kitchen scale 18, essentially without friction, anddepresses the scale, thereby registering the depressing force as aweight.

Table I tabulates the results of test conducted on prior artcommercially available blowers.

TABLE I (Prior Art) Blower Brand Honda Toro Stihl Husqvarna Makita EchoTanaka Husqvarna Model No. HHB25 51984 BG86 125B BHX2500 PB-2555 PROTHB425BVS ES 251ON Engine Honda Toro Stihl Husqvarna Robin- Echo TanakaHusqvarna Subaru 2 or 4 cycle 4 stroke 2 stroke 2 stroke 2 stroke 4stroke 2 stroke 2 stroke 2 Stroke Internal Diameter 65 66 66 68 68 68 6968 of Tube (11) in mm Engine Capacity 25 25.4 27.2 28.0 24.5 24.5 24.025.4 (cc) Overall Weight 5.028 5.069 4.460 4.360 4.72 4.736 3.8 4.371 ofBlower Kg Fan Diameter 175 162 166.5 162.7 180 158 177.7 178.5 mm FanRotation ACW ACW CW CW ACW ACW ACW ACW No. of Fan 14 9 14 13 9 15 10 9Blades Max. Height of 25.0 mm 27.0 mm 28.0 mm 24.5 mm 22.0 mm 28.0 mm24.0 mm 24.5 mm Blades (Measured Parallel to Axis of Crankshaft)Measured Kg Air 1.45 kg 1.37 kg 2.01 kg 1.71 kg 1.45 kg 1.84 kg 1.53 kg1.60 kg Thrust @ 100 mm Thrust Thrust Thrust Thrust Thrust Thrust ThrustThrust with One Blower Tube (12) Fitted Measured Engine 7000 7800 72007300 7040 6480 6600 7350 RPM@max Thrust With No No No Yes No No No NoS-shaped Chicane Offset to Align Tube with Handle Blade Curvature F F FF RADIAL* F RADIAL* RADIAL* @ fan OD (F- Forwards) (B- Backwards) *Aradial blade has its outer end substantially normal to the tangent tothe fan circumference.

In order to provide a suitable direct comparison, the inventorsconstructed two prototypes for each of two representative engines. Eachfirst prototype had an air exit which was in-line with the blower fanand thus not aligned with the blower handle. Each second prototype hadan S-shaped chicane twist so that the air exit was not aligned with theblower fan but was aligned with the blower handle. The firstrepresentative engine was the Toro two stroke 25.4 cc engine and thecomparative results for the two stroke powered prototypes and the twostroke powered prior art blower are as set out in Table II.

TABLE II (TWO STROKE) Blower Brand Toro Notaras Notaras Model No. 51984Prototype #22 Prototype #22CT (No Chicane) (with Chicane) Engine ToroToro Toro Same Engine Yes Yes Yes 2 or 4 cycle 2 stroke 2 stroke 2stroke Internal Diameter of 66 67 67 Tube (11) in mm Engine Capacity(cc) 25.4 25.4 25.4 Anti-Vibration Handle No Yes Yes Overall Weight of5.069 3.930 4.035 Blower Kg Fan Diameter mm 162 182.5 182.5 No. of FanBlades 9 7 7 Max. Height of Blades 27 mm 40 mm 40 mm (Measured Parallelto Axis of Crankshaft) Measured Kg Air Thrust 1.37 kg 2.19 kg 1.96 kg@100 mm with Thrust Thrust Thrust One Blower Tube (12) Fitted MeasuredEngine RPM@ 7800 6970 7000 max Thrust Blade Curvature @ F B B fan OD(F-Forwards) (B-Backwards) With S-shaped Chicane No No Yes Offset toAlign Tube with Handle Same Engine % increase N/A 59.9% 43% Air Thrust

The second representative engine was the Honda four stroke 25 cc engineand the comparative results for the four stroke or four cycle poweredprototype are as set out in Table III.

TABLE III (FOUR STROKE) Blower Brand Honda Notaras Notaras Model No.HHB25 Prototype #44 Prototype #44CT (No Chicane) (with Chicane) EngineHonda Honda Honda Same Engine Yes Yes Yes 2 or 4 cycle 4 stroke 4 stroke4 stroke Internal Diameter of 65 67 67 Tube (11) in mm Engine Capacity(cc) 25 25 25 Anti-Vibration Handle Yes Yes Yes Overall Weight of 5.0283.980 4.085 Blower Kg Fan Diameter mm 175 185 185 No. of Fan Blades 14 88 Max. Height of Blades 25.0 mm 40 mm 40 mm (Measured Parallel to Axisof Crankshaft) Measured Kg Air Thrust 1.45 kg 2.18 kg 2.05 kg @100 mmwith Thrust Thrust Thrust One Blower Tube (12) Fitted Measured Engine7000 6900 6920 RPM@max Thrust Blade Curvature @ F B B fan OD(F-Forwards) (B-Backwards) With S-shaped Chicane No No Yes Offset toAlign Tube with Handle Same Engine % N/A 50.3% 41.4% increase Air Thrust

From the three tables it can be seen that the inventors' fans havesubstantially fewer fan blades than the prior art fans. These fewerblades have the advantage of a lesser number of noise waveforms beinggenerated. This is very advantageous in the reduction of noise which isgenerally very irritating to nearby persons. In addition, when thislower noise level is combined to a shorter overall time of use, becausethe inventors' fans have a more powerful thrust, the overall advantageover the prior art fans is considerable.

Turning now to FIGS. 5-6B, a first embodiment of the fan 7 isillustrated. The fan 7 consists of a generally flat disc 30 which istypically approximately 175-185 mm (approximately 7 inches) in diameter.This disc 30 has a central hub 31 which enables the fan to be mounted tothe output shaft of the motor, and eight upright but rearwardly inclinedblades 32 which extend generally radially but with a rearward sweeprelative to the direction of motion of the fan 7 (counter-clockwise asseen in FIG. 5).

As illustrated in FIG. 6A, each of the blades 32 has a ramp portion 34which forms the radially inner part of each blade, and a wing portion 35which forms the radially outer portion of each blade 32.

As seen in the plan view in FIG. 7, each of the blades 32, because ofits rearwardly swept nature, during rotation experiences a radiallydirected centrifugal force Fr which can be resolved into two components.These components are Fa, which is the component of the force directedalong the longitudinal axis of the blade, and Ft which is thetransversely directed component of the force which points approximatelyin the direction of rotation of the disc 30. There is also a forceopposite to the transverse force Ft which is the force of the air oneach blade, however, at the typical operational rotational speed of thedisc 30 (typically approximately 6000-8000 rpm) the transverse componentFt of the rotational force substantially exceeds the force of the air onthe blade 32. Thus the blade 32 experiences a net forward force.

Since the disc 30 is molded in a single piece from a substantially rigidmaterial, such a nylon or glass filled nylon, and the thickness of thebase of the blade 32 (typically 1.75-2 mm) is thinner than the thicknessof the disc 30 (which is typically 2.5 mm), the net forward transverseforce on the blade 32 tilts the blade 32 forwardly as indicated in FIG.6B. This forward tilt of the blades 32 in operation is illustrated inphantom in FIG. 5.

This deformation at operational speed has the consequence that thetilted blades 32 constitute an air scoop for the fan which is moreeffective than the blades 32 would be if the fan was not distorted inoperation. Preferably the maximum extent of the blades 32 in a directionparallel to the shaft of the motor is in excess of 30 mm, and preferablyin excess of 35 mm and, as indicated in the comparative Tables II andIII, most preferably approximately 40 mm.

The amount of tilt, or positive distortion, of the blades 32 depends onthe blade height, the thickness of the blades 32, the thickness of thedisc 30, and the engine speed.

Turning now to FIGS. 8-9B, it will be seen that the disc 130 of thesecond embodiment has a hub 131 and blades 132. The hub 131 includes ametal sleeve 133 which is molded into the disc 130 during itsfabrication and provides a convenient mounting mechanism whereby thedisc 130 can be mounted on the output shaft of the engine

Each of the upright blades 132 again has a ramp portion 134 and a wingportion 135, however, the blades 132 are straight (rather than beingcurved as in FIGS. 5-6B) and, as before, the blades 132 are rearwardlyswept relative to a radius of the disc 132 and its direction of motion(anticlockwise). As before, the blades 132 are subjected to therotational forces. However since in this embodiment the blades 132 arethicker and stiffer than the disc 130, it is the disc 130 which distortsto provide a more efficient air scoop than that provided by theundistorted prior art fans. This distortion of the disc 130 isillustrated in exaggerated fashion in FIG. 9B. The disc distortion alsopermits the more rigid blades 132 to tilt forwardly in the direction offan rotation somewhat without appreciable bending. This is illustratedin phantom in FIG. 8. Again the result is a more efficient air scoop.

The nature of this distortion due to rotational forces gives rise tothree possible situations, each of which is difficult to illustrate. Thefirst situation is where the upright blades 32 are relatively less rigidthan the disc 30. This has the consequence that the disc 30 does notdistort and the upright blades 32 are bent or curved so as to tiltforwardly. This is the situation illustrated in FIGS. 5-6B. The secondis where the upright blades 132 are relatively more rigid than the disc130. This has the consequence that the disc 130 distorts and the uprightblades 132 are consequently tilted forwardly. This is the situationillustrated in FIGS. 8-9B. The third situation is where both the blades32,132 and the disc 30,130 are to some extent flexible, in which caseboth the disc flexes and the blades bend forwardly and also tiltforwardly as a result of the disc flexing. This third situation is acombination of the arrangements illustrated in FIGS. 5-6B and in FIGS.8-9B. All three possibilities exist with all the types of bladesillustrated in FIGS. 5-11.

As seen FIGS. 10 and 11, it is also possible to mould the blades 232 onthe disc 230 so as to be both curved when viewed in plan in FIG. 10, andalso tilted forwardly when stationary as illustrated in FIG. 11. Thisarrangement has the disadvantage that the tilted blades 232 require amould with more expensive tooling than the moulds for the upright blades32, 132.

All of the above mentioned blade and fan configurations provide a moreeffective “scoop” and thus the above described improved fan performance.

Because these blowers have to be held by one hand, they all suffer fromthe conflicting requirements that they be sufficiently light in weightto be carried but must have a powerful thrust of air blast to have theability to easily and quickly blow the intended litter/leaves etc. Theblowers also suffer from vibration that is transmitted to the operator.Further, even those blowers of intermediate blowing thrust without achicane twist are not comfortable to use because of reaction torqueforces which the operator's wrist muscles must provide.

To be as light in weight as possible most gasoline engine have been inthe 20 cc (“small”) to 25 cc (“midsize”) engine capacity. However, withmore air thrust blowing power being required, the tendency in recenttimes is for manufacturers to use an increased capacity engines up toabout 30 cc.

However, with the increase in engine size come inevitable drawbacksincluding extra weight, extra vibration, extra engine noise, and higherfuel consumption.

Most of the gasoline engines are 2 cycle engines, with 4 cycle enginesbeing an overall smaller percentage of the market due to the 4 cycleengines of the same capacity being heavier and more expensive enginesbecause of their extra componentry.

Because these blowers are hand held, it is important for them to bereasonably balanced with the handle situated above the unit andapproximately in a centre of balance position. As a result, the blowerhousing is to one side of the centre of gravity and the engine is to theother side. Normally the blower air exit is substantially co-planar withthe plane of the fan (as illustrated in FIG. 1) since any “corner” orbend in the air flow direction would increase flow resistance and thusreduce the air thrust of the blower. However, such an air exit which isco-planar with the fan is not aligned with the centre of gravity orcentre of balance of the blower 101. Thus the air exit 111 is notaligned with the handle 103 and the air leaving the blower imparts aturning movement or torque to the blower. To prevent the blower 101twisting, the user must supply a reaction torque by a muscular twist ofthe wrist. With any consistent use this twisting of the wrist istiresome and not user friendly. To overcome this problem one majorquality brand manufacturer (Husqvarna) has an offset air exit with an“S” shaped twist, or chicane in the outlet. This results in the blower'sair exit being in line with the handle of the device.

However, this comes at a loss of air thrust due to the two bends of “S”shaped twist, which is as a comparison, like a “chicane twist” of a caror motor cycle racing circuit where chicane twists are used to reducethe speed of, and slow down, the racing participants.

In order to overcome the loss of air blowing thrust brought about bytheir chicane, it appears that Husqvarna decided on a larger than usualengine capacity by using a 28 cc 2-cycle engine. As can be seen fromcomparison Table 1, the air thrust of this Husqvarna 125B model producedonly an intermediate air thrust of 1.71 kg even with its large andpowerful 28 cc engine. Since the Husqvarna engine rotates in a clockwisedirection, its fan blades which are swept forwardly, appear at firstglance to be similar to those of FIGS. 5 and 8. However, the directionof rotation of the engine has to be taken into account when viewing thefan in order to determine whether the blades are swept forwardly, orbackwardly, relative to the direction of rotation.

Husqvarna have very recently also introduced a new hand blower model425BVS without a chicane twist, and which has a 25.4 cc engine. Itappears this new model was introduced to achieve a better air thrustoutput which was comparable with their new smaller engine, butsubstantially the same prior art fan design has been used.

An existing blower with a powerful air thrust and a quality brand is theStihl BG86 which has a large 27.2 cc engine made by Stihl. This is agood example of a high output air thrust blower that has the drawback ofthe blower always trying to twist the operator's wrist due to theoff-centre nature of the air output relative to the handle.

To overcome the problem of vibration, only two of these listed majorbrands have an anti-vibration handle, i.e. a handle that is more or lessisolated from the engine (or provides a small reduction in thevibrations felt by the operator). However, such anti-vibration handleshave the drawbacks of not only extra cost, but importantly, extraweight.

In order to ameliorate these problems, the present inventors have beenable to considerably increase the air blowing thrust, even using thesame engines of existing blowers. This then enables the use of the “S”bend (or chicane) to centre the air blowing outlet in line with thehandle, and with the ultimate savings of weight, an efficientanti-vibration handle system can be fitted. Thus the complete blowerunit of the preferred embodiments is of considerably lighter weight thanits competitors but still with very high output of air thrust with norotational torque applied to the wrist of the operator.

Thus the improved motorized hand held blower of the preferredembodiments is very comfortable to use with virtually no vibration, notwisting of the operator's wrist despite the blower's very powerful airthrust blast, and with relatively low fuel consumption due to themid-size engine fuel usage. In addition, due to its very powerful airthrust, the blower of the preferred embodiments is used for much shorterblowing operation times. This also reduces the total volume of fuelconsumed and the time during which noise is generated.

These advantages arise because of the considerably improved efficiencyof air thrust volume generated by the construction of the fan which is adeparture from the fans used by other brands.

With experimentation it has been found that the big improvement is thedimensional shape of the fan blade, the angle of the fan blade at thetangent point of the outside diameter of fan disc, the height and numberof blades, and the general 3 dimensional operational shape of the bladescaused by the distorting centrifugal force applied to the spinning disc.

Because the blower is moved from side to side (sometimes abruptly) thegyroscopic forces acting on the very high RPM fan (usually 6000 to 8000RPM) can cause problems to the fans and/or fan housing unless the fan ismade strong enough.

The fans are made of a circular molded plastics disc with blades presentnormally only on one side of the disc and extending substantiallyparallel to the axis about which the fan/disc rotates. The disc can beflat but are mostly are slightly convex with blades on the convex sideof the disc.

Usually the molded plastic fan is a one piece unit (without a metalinsert centre hub) but sometimes such a centre hub metal insert 133 isadded.

The air inlet into the blower housing chamber, which surrounds the fan,has an inlet on the blade side of the disc fan. Generally the air inletis substantially concentric with the blades/disc.

With fans of the prior art blowers, the radially innermost part of theblades is close to, or at, the centre of the disc. The blades extendradially outwardly towards to the outside diameter of the disc. Whenlooking at the disc face on, i.e. in a plan view, most prior art fanshave the blade end extending to the outside diameter of the disc and theradially outward portions of the blades facing in a forward directionrelative to the direction of rotation of the fan or disc. That is, theblade ends are swept forwardly relative to the intended direction ofrotation of the fan.

Some brands have a blade end (i.e. at the disc outer diameter) that issubstantially radial, i.e. at 90° to the OD tangent portion. None of theprior art fans have rearwardly swept blades ends.

All the prior art hand blowers also have a generally low blade height(see Table 1) of less than 29 mm and with a large number of blades, from9 to 15. This is in contrast to the preferred embodiment of the presentinvention which has a small number of blades (e.g. 7 to 10) but verytall blades by comparison at approximately 40 mm in height. A furthersubstantial difference is that for the preferred embodiment the blade isrearwardly facing or rearwardly swept. The intentionally rearwardlyfacing blades, and these blades being fewer in number, did not requireas much engine power as forwardly facing blades and therefore the bladeheight can be increased to maintain the engine loading and also increasethe air flow and thrust. Importantly, the tall blades have the abilityto change shape under the influence of centrifugal forces when rotatingat high speed from being parallel to the fan axis to tilting forward orleaning from the fan axis to form a “scoop”. This scoop furtherincreases the efficiency of the fan, and also results in a reducedvortex, or “drag”, on the trailing side of the blade. The blades can besubstantially straight and rearwardly facing (as in FIG. 8), orsubstantially arcuate and rearwardly facing (as in FIG. 5).

This forward leaning of the blade at speed is due to centrifugal forcesand can only occur with rearwardly facing, or swept, blades whichexperience a radially directed centrifugal force component. Thus theinventors have realized such blades can be designed to have the blades(32,132) intentionally proportionally tilt forwardly.

The disc diameter and/or blade length of the preferred embodiments donot change with the centrifugal force. Also the disc, (and the blades onthe one side of the disc), are strong enough to prevent any overdistortion and/or destruction from inertial forces. The spinning disc ofthe fan has a considerable rotational angular momentum. Yet the fanhousing and the blower as a whole is able to be moved quickly to and froin an arc as the operator maneuvers to sweep up debris. So the fan discmust be strong enough to resist the inertial forces it experiences andnot strike the fan housing (bearing in mind the small radial distancebetween the fan outside diameter and the fan housing and also the smalldistance between the outer edge of the fan blades and the sides of theinterior of the fan housing). This disc strength and blade strength isparticularly necessary due to the close tolerance required (e.g. betweenthe spinning blades and the air chamber housing). Any touching by thecomponents will produce significant scraping or “drag” whichsignificantly reduces output of the blower and/or melting of the plasticcomponents due to the high heat generated by the frictional forces.

As can be seen in Tables II and III the increase in air thrust of thepreferred embodiments is very dramatic. The increase in air thrust wasin the order of 60% greater for the 2 cycle Toro blower and 50% greaterfor 4 cycle Honda blower.

Because of the very efficient air output of the prototypes, savings inweight of the complete blower apparatus were achieved using the sameToro and Honda engines. Furthermore, an efficient 3 point anti-vibrationhandle system was also fitted to the respective apparatus andnotwithstanding the increased weight of the anti-vibration handles, eachcomplete blower apparatus was much lighter than the original Toro andHonda blowers (see Tables II and III).

All four prototypes, both 2 cycle and 4 cycle, and with and without withthe chicane, are lighter than all major listed brands as per Tables Iand II, except for one brand (Tanaka) with its measured low air thrustoutput of only 1.53 kg.

Except for the Stihl BG86 and Honda HHB25 blowers, none of the otherlisted brands have anti-vibration handle systems. If they did, thiswould further increase the weight of these other listed brands.

Also as a direct comparison, the Stihl BG86 blower has a large 27.2 cc 2cycle engine which is 8.7% larger in engine capacity with higher enginepower, and the Husqvarna 125B blower's 28 cc 2 cycle engine has 11.8%larger engine capacity and higher engine power, when compared, forexample, to the inventors' comparative blower with the smaller 25 cc 4stroke Honda engine that was used.

Similarly, the Stihl BG86 blower has a large 27.2 cc 2 cycle enginewhich is 7.1% larger in engine capacity with higher engine power, andthe Husqvarna 125B blower's 28 cc 2 cycle engine has 10.2% larger enginecapacity and higher engine power, when compared, for example, to theToro engine used in the inventors' 2 cycle 25.4 cc engine.

The foregoing describes only some embodiments of the present inventionand modifications, obvious to those skilled in the air blower arts, canbe made thereto without departing from the scope of the presentinvention. For example, if desired, the underside of the disc which isillustrated as having no blades can be provided with smaller additionalblades.

The term “comprising” (and its grammatical variations) as used herein isused in the inclusive sense of “including” or “having” and not in theexclusive sense of “consisting only of”.

While the principles of the invention have been described above inconnection with preferred embodiments, it is to be clearly understoodthat this description is made only by way of example and not as alimitation of the scope of the invention.

1. A portable hand-held blower comprising: a power source having an axisof rotation, a fan mounted on said power source to be driven thereby andlocated within a housing, said housing having an array of inletapertures and a single main exit, a handle atop said housing and mountedsubstantially above the centre of gravity of said blower, said main exithaving a generally S-shaped configuration to substantially align thepath of air exiting said blower with said handle to prevent a torquebeing experienced by an operator holding said handle in use, and saidfan being molded in a single piece from substantially rigid material;wherein said fan comprises: a generally flat disc each quadrant thereofhaving a plurality of generally radially extending blades which allextend on the same side of said disc, which all are rearwardly sweptrelative to the intended direction of rotation of the disc, which allextend to a predetermined height above a plane passing through said discand substantially perpendicular to said axis of rotation, said bladesbeing tilted transversely and in the direction of rotation of said faneither as a consequence of the manufacture of said blades, or as aconsequence of the forces created by the operational rotational speed ofsaid fan, and whereby each transversely tilted blade and its adjacentportion of said disc in front of each said blade forms an air scoop forsaid fan.
 2. The blower as claimed in claim 1 wherein said forces flexsaid adjacent portions of said disc in front of each said blade and eachsaid flexed portion of said disc contributes to the corresponding saidair scoop.
 3. The blower as claimed in claim 1 wherein each said bladeis manufactured to be upright relative to said disc.
 4. The blower asclaimed in claim 3 wherein each said upright blade is able to be tiltedby said forces.
 5. The blower as claimed in claim 4 wherein each saidupright blade is tilted by said forces by bending at its base.
 6. Theblower as claimed in claim 4 wherein each said upright blade is tiltedby said forces by bending above its base.
 7. The blower as claimed inclaim 1 wherein each said blade is manufactured to be tilted relative tosaid disc.
 8. The blower as claimed in claim 1 wherein said fan has aside opposite said side carrying said blades, which is free of blades.9. The blower as claimed in claim 1 wherein said blades have aperpendicular height above said disc of at least 30 mm.
 10. The bloweras claimed in claim 1 wherein said blades have a perpendicular heightabove said disc of at least 35 mm.
 11. The blower as claimed in claim 1wherein said blades have a perpendicular height above said disc of atleast 40 mm.
 12. The blower as claimed in claim 1 wherein said handle ismounted substantially above the centre of gravity of said blower.
 13. Afan for a blower, said fan comprising: a generally flat disc eachquadrant thereof having a plurality of generally radially extendingblades which all extend on the same side of said disc, which all arerearwardly swept relative to the intended direction of rotation of thedisc, which all extend to a predetermined height above a plane passingthrough said disc and substantially perpendicular to said axis ofrotation, said blades being tilted transversely and in the direction ofrotation of said fan either as a consequence of the manufacture of saidblades, or as a consequence of the forces created by the operationalrotational speed of said fan, and whereby each transversely tilted bladeand its adjacent portion of said disc in front of each said blade formsan air scoop for said fan.
 14. The fan as claimed in claim 13 whereinsaid forces flex said adjacent portions of said disc in front of eachsaid blade and each said flexed portion of said disc contributes to thecorresponding said air scoop.
 15. The fan as claimed in claim 13 whereineach said blade is manufactured to be upright relative to said disc. 16.The fan as claimed in claim 15 wherein each said upright blade is ableto be tilted by said forces.
 17. The fan as claimed in claim 16 whereineach said upright blade is tilted by said forces by bending at its base.18. The fan as claimed in claim 16 wherein each said upright blade istilted by said forces by bending above its base.
 19. The fan as claimedin claim 13 wherein each said blade is manufactured to be tiltedrelative to said disc.
 20. The fan as claimed in claim 13 wherein saidfan has a side opposite said side carrying said blades, which is free ofblades.
 21. The fan as claimed in claim 13 wherein said blades have aperpendicular height above said disc of at least 30 mm.
 22. The fan asclaimed in claim 13 wherein said blades have a perpendicular heightabove said disc of at least 35 mm.
 23. The fan as claimed in claim 13wherein said blades have a perpendicular height above said disc of atleast 40 mm.